As you all know certain antibiotics when taken orally can cause gastro-intestinal tract disturbances and sometimes it can extend to serious side effects. All these symptoms and signs occur due to the disturbance of the normal flora of the gut. As you know there are susceptible and resistant bacterias to a antibiotic of choice. When that antibiotic is administered the susceptible bacterias die or the growth is retarded. But now the resistant bacterias do not die and those have a better chance of overgrowing since all the other bacterias in the gut are less in number.
Pseudomembranous colitis
One classical example for this is Pseudo membranous colitis. It is an acute inflammatory condition of the colon where a membranous exudate is produced. Sometimes this can be lethal.
Pathogenesis of Pseudomembranous colitis
When the antibiotic Clindamycin is given to a patient most of the bacterias in the colon die except Clostridium difficile which present in very small numbers in the normal flora of a healthy individuals. Now an overgrowth of Clostridium difficile occur in the gut. Certain strains of Clostridium difficile can produce toxins.(pathogenic strains produce two toxic polypeptides,designated A and B. Toxin A is an enterotoxin that causes excessive fluid secretion , but also stimulates an inflammatory response and has some cytopathic effects. Toxin B is a cytotoxin. These toxins can cause the death of gastrointestinal epithelial cells and finally a pseudomembrane is produced. Complications include gastro-intestinal tract bleeding, perforation of the gut and peritonitis.
Treatment
Treatments include avoiding the causative antibiotic and oral metronidazole (Vancomycin is also used.)This condition is also known as antibiotic associated colitis.
Laboratory identification of Clostridium difficile
Cultured from stools using routine anaerobic procedures. Toxin can be demonstrated in stool extracts.
References
Wikipedia - Pseudomembranous colitis
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